It might be caused by international character input. For me whenever I type the a single quote (') or the double quote (") or a tilde (~) followed by certain letters it auto-corrects it into an accented character:

So:
'a => á
"a => ä
~n => ñ
"u => ü
/c => ¢
etc.

I am not sure if it is something Java is doing or if it is JEdit enabling international character input. This is under Windows XP SP2, JRE 1.5.0, Jedit 4.2. Either way, it makes writing program code a major pain.

Roger